Portable sander



April 5, 1949. G. DUFF' 2,466,584

l PORTABLE SANDER Filed Aug. 13, 1945 2 Sheets-Sheet 1 c 37 www 35 :annui Afro/aven April 5, 1949. G. L.. DUFF 2,466,584

PORTABLE SANDER Filed Aug. 13, 1945 2 Sheets-Sheet 2 J6 62 l5 I7 20 la INVENTOR. 2Q/Z6'. 4. 650,@65 @0f-'5 Patented Apr., 5, 1949 UNITED STATES PATENT OFFICE 2,466,584 PORTABLE SANDER George L. Dull, Long Beach, Calif. Application August 13, 1945, sei-m1 No. 610,585 s claims. (ci. 51-170) My invention relates broadly to sanding and polishing machines and more particularly to power-operated portable sanding machines oi the hand-propelled type.

Such machines are now commonly in use and it is the endeavor of manufacturers thereof to eliminate unnecessary vibration and to screen the moving parts and the power mechanism from the dust and grit which results from their operation. In dealing with the problem of vibration, it is desirable to have the reciprocating or oscillating parts as light as possible in proportion to the weight of the driving parts. By reducing friction, whichalso causes vibration and increases power consumption, it is possible to use driven parts of less weight as the stresses upon them are reduced. The elimination of large lubricated bearing surfaces reduces friction and also assists in the problem of dust control, focusing it upon the protection of the driving parts.

It is therefore a principal object oi myinvention to provide a sanding machine having its parts connecting the driving and driven mechanism constructed simply and effectively and combining in themselves eillcient anti-friction devices. v

It is a further object of my invention to provide a machine in which the connecting bearing surfaces will be self-screening from dust.

Still another object is to provide a machine of few reciprocating parts and those parts of simple construction and light weight.

A further object is to provide a sanding machine having means for selectively adjusting the frequency of vibration in proportion to the resistances developed by the roughness of the surface worked upon and the coarseness of the abrasive utilized.

These and other apparent objects I attain in a manner which will be clear from consideration of the following description taken in connection with the accompanying drawings, of which:

Figure 1 is a perspective view of the sanding machine of my invention showing the assembly oi' the exterior parts;

Figure 2 is a vertical section along the line 2-2 of Fig. 1;

Figure 3 is a vertical section at right angles to the view of Fig. 2 and taken along the line 3--3 thereof;

Figure 4 is a horizontal section on the line 4-4 of Fig. 3, with parts shown in plan to illustrate exterior and interior assembly;

Figure 5 is a fragmentary section on line 5-5 u handle I2, and a base I3.

5 ing mechanism.

Considering now the aforesaid drawings in detail. I have designated by the numeral Il) a housing unit which may be cast in one piece and which comprises a hollow motor housing II, a The motor housing II houses a motor I4, access to which is obtained through an opening I5, normally closed by a cover plate I6, which may be held in place by screws I'I. The handle I2 has an interior chamber I8 in which is housed a switch I9, the electrical conduits for which emerge to the motor through a passage 2n and to a source of power through a passage 2I. The switch I9 is operated by a trigger 22 extending through an opening 23 on the inside of the handle I2, and access to the switch is provided through an opening 24 on the outside of the handle normally closed by a cover plate 25. The base I3 has an opening 26 for receiving the motor during assembly,.and

a second opening 21 below the handle I2 for access to the parts carried therebelow and closed with a cover plate 28 held by spring flanges 28 to aid its ready removal and replacement. The lateral margins of the base I3 are rabbeted on 30 their lower edges to form recesses 30 for holding members of the hereinafter described bearing mechanism.

A plate 3l of slightly greater length than the' housing unit III, and of the same width, extends therebeneath. On the upper side of the plate 3l are lateral ribs 32 and end ribs 33'forming an v*open-topped box, the end ribs 33 having out, wardly turned flanges 34. The plate haslongitudinal extensions 35 beyond the end ribs33, and

lateral extensions beyond the lateral ribs 32 terminatinglin upturned flanges 36. Clamping bars .'ll are mounted in the recesses formed at each end of the plate 3l by the extensions 35 and the 33'.l A sheet of sand paper of buing cloth 39 may be stretchedfacross the bottom of the plate- 5 unit I0, I provide an eccentric 40 mounted on lthe motor shaft 4I, and held thereto by a setscrew 42. A pitman 43 engages the eccentric 44 with ball-bearings 44, held in place and protected against dust by a cover plate 45. The other end oi' the pitman 43 engages a pin 46 flanges 34, being held therein by bolts orscrewsgwhich is formed integrally with ,a plate I1 and extends therethrough into a boss 4l on the plate 3|. The plate I1 is further held inrigid engagement with the boss 4l by a screw Il.

To support the motor il within the motor housing Il and to protect the motor from dust. I provide a support plate Il held in place against the motor housing il by screws Il, and thickened centrally to provide a bearing l2 for the motor shaft 4I. The bearing may be provided with anti-friction devices if desired.

The action of the eccentric 4l and the pltman 43 will cause the plate 3l to have reciprocating motion with respect to the unit il. To connect the unit Il to the plate Il with guide surfaces of low friction I provide ball-bearings of rec-y tilinear type, the races of which are so positioned that the balls actas the connecting means between` the unit." and-the plate ll in'addition to their .function of absorbing pressurebetween these parts. Bars I3 are attached to the housing unit I l in the recesses 3l by. means of screws Il,

iltting snugly within the recesses, the ends of which fit around the ends of the bars.` A pore tion of each of the bars I3 extends downwardly below the respective recess and has a longitudinal groove 55 onits inner face. `Similar bars Il are held by screws i1 to the lateralribs I2 of the plate 3l with grooves Il in their outer sides and co-extensive with the grooves l5. Both sets of bars I3 and it are shorter than the lateral ribs I2 by an amount slightly greater than the length of travel of the plate 3i as caused bythe eccentric Il, so that the movement of the plate 3l relative to the unit il does not bring the end ribs Il into contact with the bars I3. The end ribs il extend outwardly to the edge of the plate 3| to form enclosures within which the relative movement of the bars 53 and 5l may take place.

The upturned ilanges I6 complete the enclosuresv and serve as dustguards.

When the unit -illis placed upon the plate ll it-wi1l, but for thebearings'now to be described, rest upon the upturned flanges 3i, with the grooves 55 and 5l not quite in horizontal'alignment and cooperating to form channels between them. In these channels I provide bearings comprising a plurality of balls separated by rollers l0. The balls I! are eter than the rollers 80, so that the latterv sustain no weight but serve as separators only, resting in the bottom of the channels formed by the grooves. The screws l1 holding the ends o f the bars 5I are longer than the intermediate screws and extend into the channels where they act as stops to limit the endwise travel of the balls and rollers and to prevent the entry of dust into the channels. Y

The diameter of the balls I9 is suiiicient to hold the innerfaces of the bars 53 from the outer faces of the bars 5i and also to hold the bars 53 from contact with the upturned ilanges The weight of the unit Il rests upon the contact points of the upper sides of the grooves I5 with the balls 59, and through the balls to the lower sides of the grooves 5t. The same series of contact points prevents lifting the unit Il from the plate 3| without ilrst removing at least one of the bars 5I. In assembling the machine, vthe unit it is placed upon the plate ll, with the bars Il in place oi the latter, and the balls andl rollers are then laid in the grooves of the bars Il which are then fastened 1in place. The only openings for dust into the channels containing the .balls are at the ends ofthe channels which are proof slightly larger diam- I control Il at its upper end 4 tectedbytheendsoftheendribsandbythe screws Il, and the narrow slots between the bars. the upper of which leads only into the enclosure betweentheunit Ilandthe plate Il andthelower of which leads into the enclosures formed by the upturned flanges Il.

In reducing vibration and in saving power which is wasted by vibration it is useful to proportion the frequency of reciprocation to the load resulting from the roughness of the surface worked upon and the coarseness of the abrasive sheet 30. To achieve this end I utilize a motor Il of thevariable speed type having a rheostat accessible when the cover plate Il is removed. Turning the control li to adjust' it is accomplished by means of a discllwhichiskeyedtothecontrolasshownat j I and hasa screw-driver slot Il in its upper face. By providing the'disc l! with an annular shoulder Il whichiits againstasimiiarshoulderinthemotor housing I I. rigidity of the motor between the support plate Il and the housing'llis also secured.

In the operation of the sanding machine, the motoris started .by pressure on the trigger Il of the switch I. Rotation oi the eccentric 4l within the :pitmanimparts a crankmotion to the pitman which in turn imparts a reciprocating motion to the plate 3l and the abrasive sheet Il attached thereto. When the machine is held against work to be smoothed, the upper element comprising the motor and the housing and handle remains relatively motionless while the lower element comprising the plate and abrasive sheet is moved rapidly back and forth. The only connecting parts between `the two elements are the balls 59 andthe pitman Il Vwhich is mounted in ballbearings Il. All stresses, due either to vibration or to reciprocation, are transmitted through balls, the rolling movement of which minimizes friction and vibration andpasses only the stressl. of reciprocation. With the undesirable stresses minimized, the operator may adjust the rheostat control Si so as to provide power to turn the motor at that speed which most eifectively deals with the remainder having regard to the roughness of the work, the coarseness of the abrasive. and the pressure' which the operator wishes to apply.

Having now described and shown my preferred form of invention, I wish it to be understood that I do not mean to be limited to the particular form or arrangement of parts herein described and shown, which ismerely illustrative of the broad principles of my invention as dened in the appended claims.

I claim: l

i. In a sanding machine having an upper element, and a lower element adapted to have endwise reciprocating motion with respect thereto, bars carried on the sides of each of said elements, the bars Vcarried by the upper of said elements being outside of and in horizontal alignment with thel bars carried bythe lower of said elements to form cooperating pairs therewith. the adjacent faces of the bars of each of said pairs having grooves cooperating to form channels parallel to the direction of reciprocation, balls carriedin each of said channels of sumclent diameter to hold said paired bars apart and to provide support between the lower surface of the groove of any of said bars and the upper surface of the groove of the cooperating bar, end portions on said lower element extending beyond and outwardly around the ends of said bars, and upwise reciprocating motion with respect thereto,

bars carried on the sides of each of said elements, the bars carried by the upper of said elements being outside of and in horizontal alignment with the bars carried by the lower of said elements to form cooperating pairs therewith, the adjacent faces of the bars of each of said pairs having grooves cooperating to form channels parallel to the direction of reciprocation, balls carried in each of said channels of sufficient diameter to hold said paired bars apart and to provide support between the lower surface of the groove of any of said bars ,and the upper surface of the groove of the cooperating bar, end portions on said lower element extending beyond and outwardly around the ends of said bars, and upwardly extending anges on the said lower element, said end portions and said anges being free of contact with said bars but closely cooperating therewith to form a relatively dustproof enclosure, and means within said channels closing the ends thereof against the exit of the said balls therefrom and the entrance of dust thereto.

3. In a sanding machine having an upper power element and a lower element adapted to have end-wise reciprocating motion with respect thereto, the combination of: bars carried by said elements arranged in side-by-side pairs and grooved in their adjacent faces to form a channel between the bars in each of said pairs, one bar of each of said pairs being secured to one of said elements and the other bar in said pair being secured to the other of said elements; balls in said channel of suiiicient diameter to hold said paired bars apart and form a rectilinear ballbearing support for said power element; and end portions and vertically extending anges on one of said elements, said end portions and anges being free of contact with said bars, but closely cooperating therewith to form a relatively dustproof enclosure.

4. In a sanding machine having an upper power element and a lower element adapted. to have endwise reciprocating motion with respect thereto, the combination of: bars carried by said elements arranged in side-by-side pairs and grooved in their adjacent faces to form a channel between the bars in each of said pairs, one bar of each of said -pairs being secured to one of said elements and the other bar in said pair being secured to the other of said elements; balls in said channel of suiicient diameter to hold said paired bars apart and form a rectilinear ball-bearing support of said power element; end portions and vertically extending nanges on one of said elements, said end portions and iianges being free of contact with said bars, but closely cooperating therewith to form a relatively dust-proof enclosure; a rotary power shaft extending from said upper element downwardly into said enclosure; an eccentric nxed on said shaft and positioned below a plane dened by said bars; and a connecting rod connected between said eccentric and said lower elements whereby to drive said lower element in reciprocating motion with respectto said upper element.

5. In a sanding machine having an upper element and a lower element adapted to have endwise reciprocating motion with respect thereto, the combination of bars carried on the sides of each of said elements, said bars being arranged in pairs in side-by-side relationship and in horizontal alignment with the adjacent faces of pairs of said bars having grooves therein cooperating to form channels parallel to the direction o1 reciprocation; balls carried in each of said channels of suiiicient diameter to hold said paired bars apart and to provide support between the lower surface of the groove of any of said bars and the upper surface of the groove of the cooperating bar; end portions on said lower element extending beyond and outwardly around the ends of said bars; and upwardly extending flanges on the lower elements, said end portions and said fianges being free of contact with said bars, but closely cooperating therewith to form a relatively dust-proof enclosure.

6. In a sanding machine having an upper element and a lower element adapted to have endwise reciprocating motion with respect thereto, the combination of: bars carried on the sides of each of said elements, said bars being arranged in pairs in side-by-side relationship and in horizontal alignment with the adjacent faces of pairs of said bars having grooves therein cooperating to form channels parallel to the direction of reciprocation; balls carried in each of said channels of suilicient diameter to hold said paired bars apart and to provide support between the lower surface of the groove of any of said bars and the upper surface of the groove of the cooperating ar; end portions on said lower element extending beyond and outwardly around the ends of said bars; upwardly extending :flanges on the lower elements, said end Vportions and said anges be free of contact with said bars, but closely cooperating therewith to form a relatively dust-prooi' enclosure; a rotary power source in said upper element having a shaft extending downwardly into said enclosure; an eccentric iixed on said shaft and positioned below a plane dened by said bars; and a connecting rod connected between said eccentric and said lower element whereby to drive said lower element iny reciprocating motion with respect to said upper'element.

GEORGE L. DUFF.

REFIERENEES @FEED The following references are of record in the iile of this patent:

UNITED s'ra'rns PATENTS ehi@ 12, 39S@ 

